Treatment of monkeys with various carcinogens will continue and as tumors are available potential biological markers for various types of tumors will be investigated. Treatment of monkeys with liver tumors will be continued with various anticancer drugs by both the i.v. route and intraarterial infusion. Studies will continue on the correlation of production of AFP in monkeys with the time of appearance of tumor and with histopathological changes in the liver and in the tumor. Studies of AFP synthesis by tumor cells in vitro will continue. Attempts will continue to develop primate tumor models for esophageal, stomach and colon cancer and to assess various biological markers in these model systems.